The invention relates to over-voltage circuitry and more specifically to transistor over-voltage circuitry.
Electrical circuitry utilized in a variety of applications is designed to satisfy certain operational characteristics such as voltage and current values. Naturally, inherent limitations exist in the associated circuitry that must be carefully adhered to in order to avoid failure. Typically, additional components that absorb excess voltage are used to protect main circuitry devices. Alternatively, a variety of cut-off devices that temporarily unload the protected circuit while excess power dissipates have also been proposed. Other variations, usually focusing upon tolling the input of absorbing the output are also known.
RF power amplifiers perform well when their outputs are properly terminated. In conditions of infinite VSWR (open or short circuited) the output transistors fail unless properly protected. Circulator devices located between the power amplifier and the RF output port insure a proper output load. Unfortunately, circulators are not practical at lower RF frequencies thus necessitating the use of push-pull amplifiers in order to provide over-voltage protection. The push-pull amplifier solution is ill-suited for applications involving multiple octaves and low power level.
Thus, there currently exists a need for improved over-voltage protection means in specialized applications.